If you are listed as an owner in a group, you can add or delete people from the group.  However, you must use a Windows computer to modify the group.

1. Right-click on the Start menu icon and choose Open Windows Explorer.

2. In the window that pops up, type in the word network in the bar, and press the Enter button.

3. In the window that comes up, click on Search Active Directory.

4. In the Find Users, Contacts and Groups window that comes up, type in the name of the group in the Name: field and press the Enter button.

5. Double-click on the group name.  In the Properties window that pops up, you will be able to add or remove people from the group.  Press Apply and OK to finish your modifications.  Please note that there might be a delay for any changes you make, and the new results might not be available until the next day.